liter. In the 1970s, the concentration of magnesium in Chillisquaque Creek ranged from 1.50 to 9.50 milligrams per liter in the creek's filtered water and the calcium concentration ranged from 26.4 to 48.8 milligrams per liter, in filtered water. The arsenic concentration was once measured to be 77 micrograms per liter. The cadmium, recoverable chromium, and recoverable copper concentrations were each once measured to be less than 3, less than 20, and 30 micrograms per liter, respectively. The recoverable iron concentration ranged from 160 to 410 micrograms per liter. The concentrations of zinc, lead, manganese, and aluminum were less than 20, less than 50, 50, and 500 micrograms per liter, respectively. Additionally, a detectable amount of nickel was observed in the creek. Geography, geology, and climate The elevation near the mouth of Chillisquaque Creek is above sea level. The elevation of the creek's source is approximately above sea level. The gradient of the creek is about . The upper reaches of the watershed of Chillisquaque Creek are in the Muncy Hills. Montour Ridge is located to the south of the watershed. Additionally, Limestone Ridge is situated near the creek. The creek's drainage basin mainly consists of rolling agricultural land, with some forested floodplains. Much of the central part of Montour County is in the 100-year floodplain of the creek and its tributaries. In places, it has high, muddy banks, and is generally "placid", save for some riffles and gravel bars. It is rarely blocked by fences and fallen trees, but there are a few strainers. A seep is located along the creek near the Bucknell preserve and a spring is located below Pennsylvania Route 54. Chillisquaque Creek cuts a broad and almost flat valley through rock of the Hamilton Group. It is wide and rarely rises to more than higher than the creek. A 1775 map shows the creek's headwaters as being at Tilghmans Springs. However, A. Joseph Armstrong (author of Trout Unlimited's Guide to Pennsylvania Limestone Streams) was unable to find the springs. In 2021, a 1769 survey of the Tilghman estate was obtained from the Pennsylvania Archives by Tyler Dombroski. The 1769 survey indicated the location of Tilghman's Springs as modern day "Blue Springs," just north of Washingtonville Borough where PA Route 54 crosses Chillisquaque Creek. The creek is between wide and has no apparent limestone influence, despite being near Limestone Ridge and flowing through Limestone Township. Chillisquaque